In U.S. Pat. No. 3,470,978, there is disclosed apparatus for punching acoustical openings into mineral fiberboard. As stated therein, punching such acoustical openings in fiberboard had previously been accomplished commercially by using flat press plates bearing pins which were pressed into the surface of the board.
The '978 patent discloses apparatus for the continuous and rapid punching of acoustical openings into mineral fiberboard by means of a rotating drum. This rotating drum apparatus employs spaced pins which are firmly anchored in the steel drum in combination with a layer of compressed sponge rubber provided about the outer circumference of the drum. The sponge rubber layer functions by holding the fiberboard in position on the conveyor and to remove the board from the pins as they rotate away from the board.
However, the apparatus disclosed in the '978 patent employs pins which are mounted in curved metal plates. The curved metal plates require precision drilled holes of various sizes to accommodate the different pins, and the underside of the plates must be countersunk for the pin heads. The plates must also be drilled for mounting holes which are used to attach the plates to the main rotating drum. The holes for the pins must be precision-sized in order to hold the pins firmly in place. These and many other time consuming and expensive labor steps are involved in manufacturing the rotating drum fissuring apparatus. In addition, there must be spaces between the pins which limits the apparatus to forming hole patterns with spaces between the holes.
It is an object of this invention to provide a novel rotating drum apparatus for fissuring acoustical ceiling panels with unlimited pattern flexibility.
It is another object of this invention to provide a rotating drum having fissuring pins which are embedded in flexible, resilient, but incompressible, polymeric plates which surround the rotating drum.
It is still another object of this invention to provide a rotating drum having fissuring pins arranged in patterns wherein a plurality of pins are adjacent and contiguous, with varying numbers of pins in such arrangement.
It is a further object of this invention to provide a method for manufacturing the flexible, resilient polymeric plates having the fissuring pins embedded therein.